In recent years, sports such as snorkeling, bodyboarding and surfing have become increasingly popular activities, providing participants with enjoyable forms of both exercise and recreation. These activities are similar in that they all involve swimming, an endeavor which entails self-directed propulsion of an individual through the water. Most will recognize, however, that the human body is not particularly well suited for such propulsion, owing primarily to the relatively small size of human hands and feet. Hence arises a demand for accessories which increase the effective size of a swimmer's appendages so as to better accommodate the swimmer's propulsion and enhance the swimmer's maneuverability while engaging in aquatic pursuits.
Swimming accessories of the type just described typically take the form of artificial fins which attach to the swimmer's feet. Such fins, commonly known as swim fins, include a shoe portion which receives the swimmer's foot and a blade portion which provides the desired propulsive force when the swimmer kicks his or her feet. The blade portion generally extends forwardly from the shoe portion, increasing the effective size of the swimmer's foot so as to provide a suitably sized surface against which water may pass during a power stroke. One particularly popular swim fin is illustrated in U.S. Pat. No. Re.23,006 to O. P. Churchill, such patent disclosing the well-known CHURCHILL.RTM. fin. The disclosure of that patent is incorporated herein by this reference thereto.
As will be appreciated by most water enthusiasts, swim fins are commonly formed of a resilient material which allows the fin's wearer to maintain a certain amount of comfort while the fin is in use. Such fins, however, may fail to provide the swimmer with the control necessary to ensure that the swimmer achieve the desired hydrodynamic effect. To address this problem, fins are sometimes formed of a relatively stiff material, making for greater water resistance and thus an improved propulsion effect. Stiffness, however, is not an advantageous characteristic in the shoe portion of the swim fin, stiff materials tending to detract significantly from the wearer's comfort, making the fins unbearable to wear. Such fins may also result in problems related to achieving proper fit, and may interfere with blood circulation, possibly endangering the swimmer's life. What is needed is a fin which exhibits the desired stiffness characteristics in the blade portion while maintaining the desired resiliency characteristics in the shoe portion of the fin. It is therefore an object of this invention to provide a swim fin which exhibits differential stiffness characteristics so as to improve the wearer's comfort without compromising the fin's propulsion-enhancing effect.
In the past, swim fins with differential stiffness characteristics have been proposed, such fins commonly including a skeletal framework intended to reinforce the blade portion without compromising resiliency in the shoe portion of the fin. At least one known fin includes a framework which is constructed of metal strips and enclosed in a molded material such as rubber. Such an arrangement, however, presents an unacceptable risk to the wearer due to the chance of injury should the skeletal framework puncture the fin's skin. This situation is particularly dangerous in the context of aquatic sports where an injury which immobilizes the swimmer could possibly lead to the swimmer's drowning or serious bodily harm. Other problems relate to the weight of the fins and the complexity of their design.
Other differential stiffness swim fins have also been proposed wherein the blade and shoe portions are separately formed and then fastened together by way of a complementary coupling structure. Using such an arrangement it is possible to construct a fin having a shoe portion which is formed from a relatively resilient material and a blade portion which is formed of relatively stiff material, resulting in a differential stiffness composite fin. Although these fins take steps toward enhancing the wearer's comfort, several important problems remain. First, composite fins of the type just described do little in the way of providing the wearer with the necessary control over the fin's blade portion, the wearer's foot being held in position relative to the blade portion only by the resilient material which makes up the shoe portion of the fin. The blade portion may thus flex relative to the wearer's foot during a power stroke. This, in turn, leads to increased angulation of the blade and to a decrease in the fin's propulsion effect. Known composite fins also present problems related to the difficulty in producing them, owing primarily to the difficulty encountered in providing the fins with acceptable complementary coupling structure. It is therefore an object of this invention to provide a swim fin which provides the wearer with improved control over the fin's blade portion without unnecessarily complicating the manufacture of the fin.
Many known swim fins have also failed to adequately protect the wearer's foot, often leaving large portions of the foot exposed. This is especially true where the fin is designed with comfort in mind, the wearer's toes commonly being left unprotected so as to avoid covering the toes with the rigid material which forms the fin's shoe portion or blade. Exposed toes, however, are subject to the danger of being scraped or cut, an occurrence which is unnecessarily common when wearing conventional fins. It is therefore an object of this invention to provide a differential stiffness swim fin which offers improved comfort and protection, but which does not significantly detract from the fin's advantageous hydrodynamic effects.